The laboratory core will serve three functions for the program. First, the laboratory core will perform analysis of lymphocyte receptor repertoires using a method developed by Drs. Ogle, Platt, Cascalho, and West. Second, the core will obtain laboratory studies, such as measurement of viral load and autoantibody levels needed for two or more projects. Third, the core will provide a standardized review and coordination of analysis of tissue samples for diagnosis of rejection (or lack thereof), as relevant to the goals of the program or interactions between two or more projects.